Methods and apparatus for insertion of vertebral body distraction and fusion devices

ABSTRACT

An inserter can be used to implant a distractible intervertebral body fusion device into a disc space and expand the device. The inserter includes a shaft frame and a drive shaft assembly for expanding the device and a support shaft assembly for stabilizing the device extending distally from the shaft frame. A drive housing can be operably connected to the shaft frame and extend outwardly from shaft frame distal of a proximal end of the shaft frame. Drive housing can have an internal passage that provides access into the shaft frame to a proximal end of the drive shaft assembly. An actuation tool can be disposed with the drive housing with a distal end extending through the access into the shaft frame to interface with the proximal end of the drive shaft assembly such that activation of the actuation tool rotates the drive shaft assembly to expand the device.

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.13/189,410 filed Jul. 22, 2011, which is hereby fully incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to the distraction and fusion of vertebralbodies. More specifically, the present invention relates to devices andmethods for inserting and distracting vertebral fusion and distractiondevices in the body.

BACKGROUND OF THE INVENTION

The concept of intervertebral fusion for the cervical and lumbar spinefollowing a discectomy was generally introduced in the 1960s. Itinvolved coring out a bone graft from the hip and implanting the graftinto the disc space. The disc space was prepared by coring out the spaceto match the implant. The advantages of this concept were that itprovided a large surface area of bone to bone contact and placed thegraft under loading forces that allowed osteoconduction and inductionenhancing bone fusion. However, the technique is seldom practiced todaydue to numerous disadvantages including lengthy operation time,destruction of a large portion of the disc space, high risk of nerveinjury, and hip pain after harvesting the bone graft.

Presently, at least two devices are commonly used to perform theintervertebral portion of an intervertebral body fusion: the first isthe distraction device and the second is the intervertebral body fusiondevice, often referred to as a cage. Cages can be implanted asstandalone devices or as part of a circumferential fusion approach withpedicle screws and rods. The concept is to introduce an implant thatwill distract a collapsed disc and decompress the nerve root to allowload sharing to enhance bone formation, and to implant a device that issmall enough to allow implantation with minimal retraction and pullingon nerves.

In a typical intervertebral body fusion procedure, a portion of theintervertebral disc is first removed from between the vertebral bodies.This can be done through either a direct open approach or a minimallyinvasive approach. Disc shavers, pituitary rongeours, curettes, and/ordisc scrapers can be used to remove the nucleus and a portion of eitherthe anterior or posterior annulus to allow implantation and access tothe inner disc space. The distraction device is inserted into thecleared space to enlarge the disc space and the vertebral bodies areseparated by actuating the distraction device. Enlarging the disc spaceis important because it also opens the foramen where the nerve rootexists. It is important that during the distraction process one does notover-distract the facet joints. An intervertebral fusion device is nextinserted into the distracted space and bone growth factor, such asautograft, a collagen sponge with bone morphogenetic protein, or otherbone enhancing substance may be inserted into the space within theintervertebral fusion device to promote the fusion of the vertebralbodies.

Intervertebral fusion and distraction can be performed through anterior,posterior, oblique, and lateral approaches. Each approach has its ownanatomic challenges, but the general concept is to fuse adjacentvertebra in the cervical thoracic or lumbar spine. Devices have beenmade from various materials. Such materials include cadaveric cancellousbone, carbon fiber, titanium and polyetheretherketone (PEEK). Deviceshave also been made into different shapes such as a bean shape, footballshape, banana shape, wedge shape and a threaded cylindrical cage.

Such devices need to be implanted into the disc space in a minimallyinvasive manner and then distracted to expand the disc space to thedesired height. As such, a tool for implanting such devices that allowsthe distraction to be simply and accurately controlled is desirable.

SUMMARY OF THE INVENTION

An inserter can be used to implant a distractible intervertebral bodyfusion device into a patient's disc space and expand the device. Theinserter can include a shaft frame and a drive shaft assembly forexpanding the device and a support shaft assembly for stabilizing thedevice extending distally from the shaft frame. A drive housing can beoperably connected to the shaft frame and extend outwardly from shaftframe at a point distal of a proximal end of the shaft frame. Drivehousing can have an internal passage that provides access into the shaftframe to a proximal end of the drive shaft assembly. An actuation toolcan be disposed with the drive housing, a distal end of which can extendthrough the access into the shaft frame to interface with the proximalend of the drive shaft assembly such that activation of the actuationtool rotates the drive shaft assembly to expand the device.

The above summary of the various embodiments of the invention is notintended to describe each illustrated embodiment or every implementationof the invention. This summary represents a simplified overview ofcertain aspects of the invention to facilitate a basic understanding ofthe invention and is not intended to identify key or critical elementsof the invention or delineate the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of an introducer for inserting anddistracting a distractible intervertebral body fusion device accordingto an embodiment of the present invention.

FIG. 2 is a perspective view of the introducer of FIG. 1.

FIG. 3 is a top elevational view of the introducer of FIG. 1.

FIG. 4 is a side elevational view of the introducer of FIG. 1.

FIG. 5 is a side elevational view of the introducer of FIG. 1.

FIG. 6A is a perspective view of an introducer for inserting anddistracting a distractible intervertebral body fusion device accordingto an embodiment of the present invention.

FIG. 6B is a perspective view of the introducer of FIG. 6A.

FIG. 6C is a perspective view of the introducer of FIG. 6A.

FIG. 6D is a partial perspective view of the introducer of FIG. 6A.

FIG. 7 is a perspective view of an introducer for inserting anddistracting a distractible intervertebral body fusion device accordingto an embodiment of the present invention.

FIG. 8A is a partial perspective view of an embodiment of an introduceraccording to an aspect of the present invention.

FIG. 8B is a partial top view of the introducer of FIG. 8A and adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 8C is a partial perspective view of the introducer of FIG. 8A.

FIG. 9A is perspective view of a distractible intervertebral body fusiondevice according to an embodiment of the present invention in acollapsed configuration.

FIG. 9B is a perspective view of the distractible intervertebral bodyfusion device of FIG. 9A in an expanded configuration.

FIG. 9C is an exploded view of the distractible intervertebral bodyfusion device of FIG. 9A.

FIG. 9D is a partial sectional view of the distractible intervertebralbody fusion device of FIG. 9A.

FIG. 10A is a partial side view of a distractible intervertebral bodyfusion device according to an embodiment of the present invention.

FIG. 10B is a partial side view of the distractible intervertebral bodyfusion device of FIG. 10A.

FIG. 11A is a partial side view of a distractible intervertebral bodyfusion device according to an embodiment of the present invention.

FIG. 11B is a partial side view of the distractible intervertebral bodyfusion device of FIG. 11A.

FIG. 12A is a partial top view of a distractible intervertebral bodyfusion device according to an embodiment of the present invention.

FIG. 12B is a partial top view of the distractible intervertebral bodyfusion device of FIG. 12A.

FIG. 13A is a perspective view of an embodiment of a distractibleintervertebral body fusion device according to an aspect of the presentinvention.

FIG. 13B is a side view of the distractible intervertebral body fusiondevice of FIG. 13A.

FIG. 13C is an end view of the distractible intervertebral body fusiondevice of FIG. 13A.

FIG. 14A is a perspective view of an embodiment of a distractibleintervertebral body fusion device according to an aspect of the presentinvention.

FIG. 14B is a side view of the distractible intervertebral body fusiondevice of FIG. 14A.

FIG. 15 is a side view of an embodiment of a distractible intervertebralbody fusion device according to an aspect of the present invention.

FIG. 16 is a side view of an embodiment of a distractible intervertebralbody fusion device according to an aspect of the present invention.

FIG. 17A is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17B is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17C is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17D is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17E is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17F is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 17G is a partial view of a portion of an embodiment of adistractible intervertebral body fusion device according to an aspect ofthe present invention.

FIG. 18 is a perspective view of an introducer for inserting anddistracting a distractible intervertebral body fusion device accordingto an embodiment of the present invention.

FIG. 19 is an isometric view of a device for inserting an intervertebraldevice according to an embodiment of the present invention;

FIG. 19A is an isometric view of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 20 is an isometric view of the device of FIG. 19;

FIG. 21 is a side view of the device of FIG. 19;

FIG. 22 is a rear view of the device of FIG. 19;

FIG. 23 is an isometric view of a portion of the device of FIG. 19;

FIG. 24 is a cross-sectional view of a portion of the device of FIG. 19;

FIG. 25 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 26 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 27 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 28A is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 28B is a rear end view of the portion of FIG. 28A;

FIG. 28C is a front end view of the portion of FIG. 28A;

FIG. 29 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 30 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 31 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 32 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention;

FIG. 33 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 34 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 35A is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 35B is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 36 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 37 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 38 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 39 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

FIG. 40 is an isometric view of a portion of a device for inserting anintervertebral device according to an embodiment of the presentinvention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, one skilled in the artwill recognize that the present invention may be practiced without thesespecific details. In other instances, well-known methods, procedures,and components have not been described in detail so as to notunnecessarily obscure aspects of the present invention.

An introducer 100 for implanting a distractible intervertebral bodyfusion device according to an embodiment of the present invention isdepicted in FIGS. 1-5. Introducer 100 includes a body 101 including ahandle 102 and a sleeve 104. In one embodiment, handle 102 can comprisea first piece 103 of an assembly and sleeve 104 can comprise the secondpiece of the assembly. Handle includes a slot 106 for container anactuation tool 108. In one embodiment, actuation tool 108 is a powerscrewdriver such as an electric screwdriver.

A drive shaft 110 can extend through sleeve 104 between a proximal end112 of the sleeve 104 adjacent slot 106 and a distal end 114 of thedevice. In one embodiment, sleeve 104 can completely enclose drive shaft110. At proximal end 112 of sleeve 104, actuation tool 108 can connectto drive shaft 110 where drive shaft 110 extends through an opening inbody 101. Drive shaft 110 can extend out of an opening at distal end 114and include a hex to engage a worm gear, drive shaft, or other actuationmember of distractible device. In one embodiment, distal end 114 can beshaped to match a geometry of a portion of distractible device that itabuts. Introducer 100 can also include an adjustment knob 116. Asecuring shaft 118 can extend from adjustment knob 116 through sleeve104 and out distal end 114 to interface with a tapped opening in thedevice. Knob 116 can be rotated to engage securing shaft 118 within thetapped opening, to stabilize device during distraction. Drive shaft 110can extend through a slot in knob 116 such that it can rotateindependently of knob 116. In one embodiment, drive shaft 110 andsecuring shaft 118 can be disposed at opposing outer edges of a face ofthe distractible device to allow for stable rotation of the device as itis being inserted.

To implant a distractible device 10 with introducer 100, the drive shaft110 of the introducer is attached to an actuation mechanism of thedistractible device and the securing shaft 118 is secured to a tappedopening of the device by rotating knob 116 and the device is insertedbetween adjacent vertebrae of a patient. The actuation tool 108 can beinserted into the slot 106 of the introducer 100 and connected to thedrive shaft 110 at a proximal end of the sleeve 104 either before orafter the device 10 is inserted into the disc space. Activation of theactuation member 108 causes drive shaft 110 to rotate, which distractsthe device 10. Actuation member 108 can also be rotated the oppositedirection to collapse device 10. Adjustment knob 116 provides for fineadjustment of distraction. Manual rotation of adjustment knob 116rotates drive shaft 110 a discrete amount so that optimal distractioncan be obtained. Once the device is at the desired distracted height,drive shaft 110 and securing shaft 118 can be disconnected from thedevice and the introducer can be removed.

FIG. 18 depicts a variation of introducer 100 that includes additionalfeatures. Introducer 100 includes a graduated section 120 havingmarkings 121 to indicate that amount by which the distractible devicehas been distracted. As the drive shaft 110 is turned with the actuatora slider or wheel can travel along graduated section to indicate theheight of distraction as correlated to the amount that the drive shaft110 has rotated. Introducer also includes offset portion 122 of sleeve104. Offset portion 122 allows for easier insertion into the disc spaceand also allows for an impact surface 124. Impact surface 124 providesan area at which a hammer or other similar device can be used to tap theoffset shaft 122 when the distractible device is initially inserted,which provides for easier insertion of the device.

Another introducer for implanting a distractible intervertebral bodyfusion device 10 according to an embodiment of the present inventionincludes a delivery system 200 and an actuation tool 250 and is depictedin FIGS. 6A-6C. Intervertebral body fusion device 10 is depicted in FIG.6A in a compressed configuration, in FIG. 6B in a partially distractedconfiguration, and in FIG. 6C in a fully distracted position. Deliverysystem 200 includes actuation tool 250 for actuating the distraction.

To distract the device 10, a hex of device 10 is first connected to thedelivery system 200 via a socket driver on an end 201 of delivery shaft203. In order to more securely attach the device 10 and the deliverysystem 200, a threaded end 202 of delivery shaft 204 can be threadedinto a tapped hole in device 10 adjacent the hex. The device 10 can thenbe inserted into the body via a standard transforaminal lumbar interbodyfusion (TLIF) or posterior lumbar interbody fusion (PLIF) procedureusing the delivery system 200. A lateral interbody fusion through thelateral retroperitoneal corridor is another approach. The deliverysystem 200 can guide the location of the device 10 as it is beinginserted with use of handle 213.

Delivery system 200 includes a hex 215 and a circumferential groove 214at the near end of delivery shaft 204, and also has a hex andcircumferential groove (not pictured) at the end of delivery shaft 203.Once the device 10 is in the disc space, the actuation tool 250 can beconnected to the delivery system by engaging an internal hex socketdriver of the actuation tool with the hex on the end of the deliveryshaft 203, 204. In some embodiments, an internal snap ring orcircumferential spring in actuation tool 250 can engage thecircumferential groove on delivery shaft 203 to ensure that theactuation tool 250 does not become accidentally disengaged during use.

By turning the actuation tool 250, the user transmits torque down thedelivery shaft 203 to a worm drive in device 10, which distracts thedevice 10. As the delivery shaft 203 is turned, a slider 206 advancesalong threads 209 on shaft 203. The height of the device 10 as it isexpanded can be represented on the delivery system 200 by the positionof the slider 206 along the delivery shaft 204 with fiducial marks 208,as shown best in FIG. 6D. Marks 208 may be positioned at any desirableinterval along delivery shaft 204, and the slider 206 may include aviewing slot 207 for more complete viewing of the marks 208 as they arereached by slider 206. In one embodiment, each mark 208 can represent adistracted height of 1 millimeter.

Delivery system 200 can be configured so that when the device 10 reachesits maximum desired height, slider 206 abuts stop 205 so that it can beadvanced no further, thus limiting the height of the device 10. Byallowing the delivery system 200 to limit the expansion, any damage dueto excessive torque is immediately apparent in the delivery system 200,so no damage is sustained by the device 10. In another embodiment, thedevice 10 can limit its own expansion by welding two gear teeth 424, ona threaded geared sleeve that distracts the device together so that theybind with the worm when the device 10 has reached its maximum desiredheight. Similarly, in other embodiments, one or more of the gear teethcan be omitted or a small post can be inserted into the interstitialspace between two gear teeth to limit the expansion of the device.

In one embodiment, a lever for applying torque to the shaft 204 may beaffixed to the hex 215 at the end of shaft 204. The lever may be shapedand oriented such that when the device 10 is appropriately engaged withthe delivery system 200, the position of the lever allows access to theshaft 203, whereas when the device is not appropriately engaged, thelever does not allow access to the shaft 203. In another embodiment, theslider 206 may be contained with the handle 213 in order to reduce thelength of the delivery system 200. In another embodiment, a tube able tocarry loading in torsion may be implemented around one of the shafts203, 204 to add to the structural rigidity of the delivery system. Asmall foot may be affixed to the tube to additionally support theability of the delivery system to carry, and transmit, loading intorsion by and to the device. In another embodiment, the shaft of thedelivery system 200 can be curved or bayonet in shape to allowvisualization through a minimally invasive system and working channel.

The actuation tool 250 can include a recess or loop 254 that allows thatuser to spin the actuation tool 250 with a single finger and/or largegripping surfaces 251 that the user can grasp to turn the actuation tool250. In one embodiment, the loop may be lined with a slippery or bearingsurface to enable the loop to spin easily around the user's glovedfinger(s). The actuation tool 250 can also include a broad surface 253designed to receive the impact of a hammer for implantation. Recesses252 can also be included on actuation tool 250 to afford the user animproved view of the device 10 while it is being implanted. Actuationtool 250 can span both delivery shafts 203, 204 and may extend overand/or receive handle 213 of delivery system 200. In another embodiment,rather than being driven by manual actuation tool 250, the device 10 canbe driven by a powered actuation implement such as a pneumatic orelectric drill or a motorized screwdriver mechanism, which, in someembodiments, can allow the tool to be controlled remotely.

In some embodiments, the actuation tool, manual or automatic, employssensors in the device to transmit data regarding the implantationparameters and environment, such as device load and muscular tension, toan operator or operating system to improve the performance of thesurgical procedure and outcome. The delivery system could use smallstrain gauges located on the device and/or load cells attached to thedelivery shafts and actuation tool to measure loads present during theimplantation and distraction process. These gauges and/or load cellscould be monitored by a microcontroller board located on the deliverysystem and the information fed back to a monitoring computer via astandard interface such as a USB or wireless connection. Thisinformation could be used to closely monitor a procedure's progress,warn of impending problems and improve future procedures. If not fullybridged, the gauges could be configured as half bridges within thedevice and completed outside of the device. Standard signal conditioningamplifiers could be used to excite and condition the signal to yield ameasurable output of voltage and current.

An introducer or insertion tool 300 according to another embodiment ofthe present invention that can be used to place a device 12 betweenadjacent vertebra or vertebral bodies and used to distract the endplatesof the adjacent vertebral bodies is depicted in FIG. 7. Insertion tool300 can initially be used to insert a device between vertebral bodies.In one embodiment, insertion tool 300 can include a pair of parallelscrewdrivers or wrenches 302 temporarily affixed to drive screws thatdistract the device with retainers 304. In one embodiment shown in FIG.7, insertion tool 300 extends rearwardly from device 12. In anotherembodiment, insertion tool 300 may also extend distally from device 12.In such an embodiment, device 12 can include an open nose portion andrear portion to allow it to be threaded onto insertion tool 300 andinsertion tool 300 can also be used to initially distract the vertebralbodies. Optionally, the insertion tool 300 can include a single handle301 and a gear system 303 where the handle 301 has an internal gearthat, when turned, turns external gears on the shafts that turn thescrews on the device 12 as depicted in FIGS. 8A-C. Although separatedelivery devices 100, 200, 300 have been described, it should be notedthat each feature of each device could be added to any of the otherdevices.

Referring now to FIGS. 19-40, there can be seen an inserter 600 forinserting and expanding an intervertebral body fusion device in apatient according to another embodiment of the present invention.Inserter 600 generally includes a shaft frame 602, a drive housing 604,a support shaft 606 and a drive shaft 608. As can be seen most clearlyin FIGS. 25 and 26, in one embodiment, shaft frame 602 and drive housing604 can be connected by inserting a handle portion 610 of shaft frame602 into an opening in a distal end 612 of drive housing 604. Shaftframe 602 and drive housing 604 can then be secured together byinserting fasteners through aligned apertures 614, 616 in handle portion610 and distal end 612. Support shaft 606 and drive shaft 608 extendfrom a distal end 618 of shaft frame 602 for connecting to a device 10for insertion into a patient.

It can take significant force to insert an implantable device into adisc space. Often it is necessary to strike the inserter with an objectsuch as a mallet to force the implant into the disc space. Shaft frame602 can therefore include a proximal end 603 strong enough toaccommodate striking by a mallet or other object and that does notcontain any components that may be damaged by absorbing such force. Thedrive housing 604 can extend outwardly from the shaft frame 602 at apoint along the frame displaced from the proximal end 603 to avoiddamage to the drive mechanism in drive housing 604. Such a configurationalso allows for greater visualization of the procedure when workingthrough a minimally invasive working channel tube (for example, 18-24 mmdiameter) because the drive housing does not interfere with the view. Insome embodiments, the drive housing, which along with the drivemechanism can function as a handle for the inserter 600, can be orientedat an angle greater than or less than ninety degrees from the shaftframe 602 for a more ergonomic handle that allows the device to beinserted at an appropriate angle.

One embodiment of a support shaft 606 for use with inserter 600 caninclude a rod 624 as shown in FIG. 30 and a sleeve 621 as shown in FIG.29. Rod 624 can include a wider proximal portion 623, a narrower distalportion 625, and a connecting end 627. Sleeve 621 can include a threadeddistal end 620 and a connector 622 at proximal end. Distal portion 625of rod 624 can be received within sleeve 621, with connector 622 ofsleeve 621 mating with proximal portion 623 of rod 624. Proximal portion623 extends through shaft frame 602 and connects at a proximal end witha clamp knob 626. In one embodiment, proximal portion 623 of rod 624 isconnected to clamp knob 626 with a pin that extends through clamp knob626 and into rod 624. Thus, rotation of knob 626 causes rotation ofsupport shaft 606.

In one embodiment, drive shaft 608 can include a sleeve 630 (FIG. 31), adrive link 632 (FIG. 32), a pair of joints 634 (FIG. 27) and a driver636 (FIG. 33). As can be seen in FIGS. 19-21 and 34, a first joint 634Acan extend distally from shaft frame 602. Each joint 634 can haveconnector ends 638, 640 connected by a pivot joint 642. Second connectorend 640 of joint 634A can extend into sleeve 630. Drive link 632 canextend through sleeve 630 and between first joint 634A and a secondjoint 634B. As shown in FIG. 34, which is shown without sleeve 630 forthe sake of clarity, a recessed portion 644 of drive link 632 can have aspring 646 disposed thereon. In addition, first joint 634A can include aslot 641 to which drive link 632 is attached with a pin 633 to allowlongitudinal movement of drive link 632 that is biased by a biasingmember, such as spring 646. In one embodiment, second joint 634B doesnot include such a slot, and is connected to the distal end of drivelink 632 with a pin 633 that extends through a conforming aperture.First connector end 638 of second joint 634B can connect to driver 636.This configuration of drive shaft 608 allows a single drive shaftconfiguration to have the rotational and longitudinal flexibility to beused to expand implantable devices of various sizes and configurations.

A device interface 648, shown in detail in FIGS. 28A-28C, can bepositioned at a distal end of shafts 606, 608. Device interface 648 caninclude an upper, support shaft aperture 650 and a lower, drive shaftaperture 652. An upper distal surface 654 of interface 648 can conformto a shape of a device 10 to be inserted as shown in FIGS. 35A-B. In oneembodiment, a plurality of differently configured device interfaces canbe provided with inserter 600 such that a particular device interfacethat conforms to a particular device to be inserted into a patient canbe selected for a procedure. Threaded distal end 620 of sleeve 621 canscrew into a first threaded portion of upper aperture 650. Connectingend 627 of rod 624 can then extend through sleeve 621 and first portionof upper aperture 650 and through a second, narrower portion of upperaperture 650, as shown in FIG. 35B, to attach and connect directly todevice 10. A gem nut 656 can be threaded onto the threaded distal end620 and used to tighten the connection between the device interface 648and shaft 606 with device 10. Driver 636 can extend through the loweraperture 652 through device interface 648 to connect drive shaft 608 tothe device 10. Driver 636 can be connected to a drive mechanism of thedevice 10, such that rotation of driver 636 causes expansion of device10. A bushing 658 can extend through aperture 652 to aid in securing theconnection. In one embodiment, device interface 648 is customized to beshaped to interface with a particular implantable device 10 and can beinterchangeable with other device interfaces for use with implantabledevices of other configurations. Driver 636 and bushing 658 can also becustomized for use with a particular implantable device 10. In oneembodiment, driver 636 and bushing 658 are formed as unitary componentsof device interface 648.

Shaft frame 602 of inserter 600 can also include a height indicatingmechanism that indicates and can restrict a height of the expandeddevice as it is expanded with the drive shaft 608. A cover plate 660(FIG. 37) having height markings 662 and an elongate slot 664 can bepositioned on one or both sides of shaft frame 602. Within frame 602 asshown, for example, in FIG. 36, a threaded shaft 666 (FIG. 38) canextend behind the cover plate 660. Threaded shaft 666 can included athreaded body 668 between a proximal end and a distal end. Distal endcan include a connector 670 that extends through the shaft frame 602 forconnection with the first joint 634A of drive shaft 608. Threaded shaft666 can therefore also be considered a part of the drive shaft 608assembly. An indicator nut 672 (FIG. 39) can be threadably receivedalong threaded shaft 666, such that rotation of threaded shaft 666causes the indicator nut 672 to advance along the shaft 666. Aprojection 674 can extend outwardly from indicator nut 672 through slot664 in cover plate 660 to indicate the height of the distracted device10.

Inserter 600 can also include a block stop 676 for limiting the amountby which the inserter 600 is capable of expanding the implantabledevice. Block stop 676 (FIG. 40) can include a stop 678 and a pair ofprojections 680. Block stop 676 can be slidably attached to frame 602 byinserting fasteners through a frame slot 682 through frame 602 andapertures 684 through stop 678. Projections 680 can extend outwardly ofslots 664 in cover plates 660 to provide an indication of a desiredand/or maximum implant distraction height. A knob 686 can be used totighten block stop 676 to fix it in the desired position. As the driveshaft 608 is rotated to expand the implantable device the indicator nut672 translates along the threaded shaft 666. When the indicator nut 672reaches the block stop 676, the stop 678 provides a mechanical stop thatblocks the indicator nut 672 from moving further forwards, effectivelylocking the drive shaft 608 from being further rotated to expand theimplantable device 10 beyond the maximum setting.

A proximal end of threaded shaft 666 can be attached to a shaft gear688, such as, for example, a bevel gear. Shaft gear 688 can interfacewith a corresponding drive gear 690 as shown in FIG. 36. Drive gear 690is connected via a linkage 692 to a drive mechanism 694 or actuationtool. In one embodiment, drive mechanism 694 can be retained in drivehousing 604 with a locking tab 697. Locking tab 697 can comprise twohalves with a slit therebetween. To retain an actuation tool 694 such asa screwdriver, the tool is inserted into housing and then a lockingscrew can be inserted into an aperture 699 extending through locking tab697 to forcibly retain the tool in the housing 604. In anotherembodiment, drive mechanism 694 can be retained within device 600 bydrive housing 604 and latch 696 as shown in FIG. 19A. Controls 698 canbe used to operate drive mechanism 694. Activation of drive mechanism694 causes rotation of drive gear 690, which interfaces with thecorresponding shaft gear 688 to translate the rotation to drive shaft608. As such, activation of drive mechanism 694 causes expansion of animplantable device connected at the distal ends of drive shaft 608 andsupport shaft 606.

Drive mechanism 694 can be, for example, an electric screwdriver. Inother embodiments drive mechanism 694 can be any tool that can providefor rotation of drive gear 690 and can be powered manually or by othersources, such as air power. In some embodiments, the handle of thedevice can incorporate a clutch mechanism allowing the drive mechanismto be selectively engaged with the drive shaft. Clutch mechanism allowsthe RPM's and torque of the drive mechanism to be varied because driveportion of drive mechanism can be connected to drive shaft via clutchsuch that they spin at the same speed or at different speeds or can bedisengaged such that activation of drive mechanism does not cause driveshaft to rotate at all. This provides for easy substitution of differenttypes of drive mechanisms, such as battery, electric, gas, air ormanually powered mechanisms, such as screwdrivers, for rotating driveshaft. Control of the torque delivered by drive mechanism also reducesthe risk of implant breakage and damage to the vertebral end plates ofthe patient.

In operation, an implantable device of a desired size and configurationis selected. A conforming device interface 648 can then be attached to adistal end of support shaft 606 and drive shaft 608. The implantabledevice is connected to the inserter by tightening connecting end 627 ofrod 624 into an aperture in device with knob 626. The driver 636 ofdrive shaft 608 can be connected to a drive mechanism of the implantabledevice. A desired maximum allowable height for the implantable devicecan be set by sliding block stop 676 within slot 682 on shaft frame 602to a desired height indicated on cover panel 660. A drive mechanism 694such as an electric screwdriver can be actuated to rotate drive shaft608 to expand the implantable device. The height of the implantabledevice as it is expanded is indicated by the indicator nut 672 advancingalong the slot 664 in the cover plate 660. When the implantable devicehas reached its maximum allowed height, the block stop 676 will preventthe drive shaft 608 from rotating to further expand the device.

Referring to FIGS. 9A-9C, there can be seen a distractibleintervertebral body fusion device 400 adapted for implantation into anintervertebral disc space of a patient according to an embodiment of thepresent invention. FIG. 9A shows the device 400 in a fully compressedconfiguration, FIG. 9B shows the device 400 in a fully expandedconfiguration, and FIG. 9C shows an exploded view of the device 400.Introducers as described herein can be used to insert the device 400between adjacent vertebrae of a patient and distract the device toexpand the disc space.

Device 400 includes a first member 410 having a bearing surface 402configured to interface with an end plate of one of a superior or aninferior vertebra of the intervertebral disc space and a second member450 having a bearing surface 404 configured to interface with an endplate of the other of the superior or inferior vertebra. In oneembodiment, the bearing surfaces 402, 404 can include a texturedsurface, such as that provided by corrugations 414, to create frictionwith the end plates of the vertebra to prevent accidental extrusion ofthe device 400. The radii of the corrugation 414 valley and thecorrugation 414 top width can be maximized to minimize the notch factorand reduce stress while still providing a corrugation design thatreduces the propensity of the device 400 to extrude from the disc space.One or both of the members 410, 450, can also include an opening 473,453 extending through the member for facilitating bone growth throughthe device 400. In other embodiments, opening can be filled with a gel,rubber, or other complaint material that can replicate the nucleus of anintervertebral disc and supplement the strength of the device incompressive, shear, and torsional loading conditions. Alternatively, agenerally solid surface, a textured or etched surface, a scored ornotched surface, or a surface with multiple openings can be provided oneach member 410, 450.

Device 400 can also include a pair of coaxial screw gear sleevemechanisms including threaded post members 411, 412 extending from firstmember 410 and a pair of threaded geared sleeves 420, 430 configured tosurround the post members 411, 412. Threaded post members 411, 412 canhave threads 413, 415 defined on an exterior surface thereof. Threadedgeared sleeves 420, 430 can have both interior threads 422, 432configured to interface with the threads 413, 415 of threaded postmembers 411, 412 and exterior threads 421, 431. In one embodiment, boththe exterior 421 and interior 422 threads of one of the sleeves 420 areof an opposite hand to the threads 431, 432 of the other sleeve 430.External threads 421, 431 of sleeves 420, 430 can have gear teeth 424,434 cut into the thread. In one embodiment, the gear teeth 424, 434 arenot cut down to the root, or minor diameter, of the threads 421, 431 inorder to maximize the strength of the threads. In the compressedconfiguration, threaded geared sleeves 420, 430 can fit within sleeveopenings of 461, 462 in second member 450. Openings 461, 462 can includethreaded portions 451, 452 that mesh with exterior threads 421, 431 ofthreaded geared sleeves 420, 430. In one embodiment, sleeve openings461, 462 extend all the way through bearing surface 404 of second member450. In some embodiments, as pictured, threaded geared sleeves 420, 430can be substantially solid. In other embodiments, threaded gearedsleeves can include one or more slots through the sleeve for massreduction and material savings or to promote bone in-growth.

The device 400 can be expanded with the aid of a worm 440 that extendsthrough a worm aperture 454 in the device 400 and can be driven with anintroducer as described herein. The worm 440 can have first 442 andsecond 441 opposing threaded sections configured to interface with theexterior threads having gear teeth 424, 434 of threaded geared sleeves420, 430 through a pair of apertures 457, 458 in threaded portions 451,452 of sleeve openings 461, 462. The worm 440 can include a hex 443, 444at each end of the worm 440 that allows it to be driven by anintroducer/delivery system. Such a delivery system can also be attachedto the device 400 when driving the worm 440 at tapped hole 456A ortapped hole 456B to stabilize the delivery system. Device 400 caninclude a hex 443, 444 and tapped hole 456A, 456B at each end of device,so that the device 400 can be inserted and driven from either end, orcan include a hex and tapped hole at only one side of the device,limiting the device to insertion and distraction from a singledirection. Bottom member 450 can also include one or more scallops 455above the worm aperture 454 that provide increased strength andthickness while still allowing the threaded geared sleeves 420, 430 torotate. Further detail regarding distractible intervertebral body fusiondevice such as device 400 can be found in U.S. Patent ApplicationPublication No. 2011/0160861, which is hereby incorporated by referenceherein.

A partial sectional view of a distractible intervertebral body fusiondevice 400 in FIG. 9D, helps illustrate how the device can employmultiple coaxial screw gear sleeve mechanisms as telescoping mechanismsutilizing the threaded post members 411, 412, threaded geared sleeves420, 430 and the worm 440 to expand the first member 410 and secondmember 450 relative to each other. By turning hex 444 counterclockwise,and therefore the worm 440 counterclockwise, first threaded section 442of worm 440 pulls the gear teeth 434 of threaded geared sleeve 430towards the hex head 444. This causes the sleeve 430 to translate upwardfrom the second member 450 along internal threads 452. As the sleeve 430rotates while it translates upward, the threaded post member 412extending from the first member 410, which is unable to turn, alsotranslates upward with respect to the sleeve 430 and the second member450. This second translation results from the opposite handed externalthreads 415 of the threaded post member 412 being driven by the matchinginternal threads 432 of the sleeve 430. The same mechanics are occurringon the other side of the device with oppositely threaded sleeve 420having external threads 421 and internal threads 422, post member 411having external threads 413 and second threaded section 441 of worm 440.

Because the threads for like components for each device are oppositehanded, the threads 442 on one side of the worm 440 will be pulling thegear teeth 434 of the threaded geared sleeve 430 while the threads 441on the other side of the worm 440 will be pushing the gear teeth 424 onthe other sleeve 420, or vice versa depending on the direction ofrotation of the worm 440. These opposing forces applied to the worm 440by the threaded geared sleeves 420, 430 are carried in either tension orcompression by the worm 440. Therefore, the worm 440 is notsubstantially driven into or out of the worm aperture 454 as the device400 is expanded or contracted. This is advantageous in that a pin orother retainer is not required to retain the worm and balance the forcesin the device. Such a pin can be a point of excessive wear which cancause the life cycle of the device to be shorter lived. In someembodiments, a pin can be employed to prevent the worm 440 from beingable to be pulled or pushed axially, which can cause the device tobecome jammed.

Alternative drive mechanisms to worm drive include piezoelectricactuators and any momentum imparting collision mechanism orconfiguration. Additionally, a drive mechanism, such as a worm, could bean integrated part of a delivery system or introducer. In such anembodiment, the external threads of the threaded geared sleeves wouldboth be of the same hand and the worm would be screwed into thecompressed device in the worm aperture. As the worm is turned, the axialposition of the worm would be constrained by the delivery system,instead of a pin, resulting in distraction of the device. Once thedevice reached the desired height, the worm could be screwed out of theworm aperture and the device could be locked in place by screwing in athreaded locking worm. The locking worm could have an additionalthreaded or snapping feature that enables it to be permanently, or in aremovable fashion, attached to the device. The locking worm could bemade from a radio transparent material such as PEEK, which wouldtherefore allow imaging through the worm. The locking worm would onlyneed to be strong enough to inhibit the threaded geared sleeves fromturning into or out of the device, and would not need to be strongenough to cause the device to distract. A larger radio transparentwindow could be formed by removing a portion of the sides of the bottommember on either side of the opening in the bottom member along thelength of the device, so long as the device retained a necessary amountof stiffness.

Referring now to FIGS. 10A and 10B, a preferred fit of gear teeth 424,434 of threaded geared sleeves 420, 430 in internal threaded portions,451, 452 of second member 450 is shown. As the gear teeth 424, 434 arethrust towards the internal threads 451, 452 of the second member 450 bythe worm, the load between the gear teeth 424, 434 and threads 451, 452is balanced by the bearing surfaces 463, 464 between the components,which results in the ability of the device 400 to distract a substantialload. This fit between the gear teeth 424, 434 and the internal threads451, 452 can be contrast with the fit shown in FIGS. 11A and 11B. Inthose figures, when the gear teeth 424′, 434′ of the threaded gearedsleeves 420′, 430′ are thrust towards the internal threads 451′, 452′ ofthe second member 450′, the force is not balanced by bearing surfaces asin FIG. 2B, but by the force the internal threads 451′, 452′ apply tothe gear teeth 424′, 434′. This can result in the gear teeth 424′, 434′acting as a wedge and becoming jammed against the internal threads 451′,452′, which dramatically reduces the ability of the device to distractsubstantial loads and makes the device more sensitive to frictionbetween components. Optionally, a liquid or gas lubricant, such assilicon lubricant, may be used to reduce friction in the mechanism.Saline may also be used as a lubricant.

It should be noted that although the threads depicted in the Figures areall screw threads in the form of projecting helical ribs, “thread” forthe purposes of the present invention can also refer to any othermechanism that translates rotational force into translational orlongitudinal movement. For example, in some embodiments threads can becomprised of a recirculating or spiral arrangement of bearings or anyother low friction arrangement, such as cooperating magnets.

In one embodiment, the height of the device 400 between the bearingsurfaces 402, 404 in the fully compressed configuration is 6.5millimeters and the maximum fully distracted height is 12 millimeters,thus providing a very large amount of distraction relative to theinitial height of the device. The maximum height is defined by thelargest height at which the device can meet the dynamic compressive,shear, and torsional requirements for implantable intervertebral bodyfusion devices. Variables that determine this height include the widthof the threaded geared sleeves, which is limited by the desired width ofthe device, and the material from which the device is made. With regardto the material for the device, materials with higher fatigueperformance allow the maximum height of the device to be taller evenwith a narrower width. In one embodiment, the device is made fromtitanium. The device may also be made from cobalt chrome, MP35N, orPEEK, for increased strength characteristics or increased radiolucentcharacteristics, depending on the material. X-ray transparency is adesirable property because it allows for the fusing bone to be imagedthrough the device. In one embodiment, the device can be designed suchthat in the compressed configuration the threaded geared sleeves projectthrough the bearing surface of second member in order to provide for aneven greater amount of distraction. To accommodate the device onimplantation, openings configured to contain the projecting portions ofthe sleeves can be cut into the adjacent vertebral end plate.

Once distracted, device 400 does not require a locking mechanism tomaintain the desired height within the body. This is because, whendriven backwards, the device exhibits a very high gear ratio whichcauses even the slightest friction in the system to overwhelm any amountof compression, torsion, or shear loading that might be applied to thedevice. In dynamic testing in shear, torsion, and compression, themaximum amount by which the height of the device changed was byapproximately 0.01 millimeter. The device 400, because height can bemaintained at any point along the threaded geared sleeves, thereforealso exhibits very high resolution height control, on the order of 1micrometer.

In one embodiment, the external threads 421, 131 and gear teeth 424, 434on the threaded geared sleeves 420, 430 can be substantially trapezoidalin shape. In one embodiment, the thread is a trapezoidal 8 millimeter by1.5 millimeter metric thread. A trapezoidal design enables a relativelylarge gear tooth size and, accordingly, a larger area over which thedistraction loading is distributed. Additionally, with precisemanufacturing, multiple gear teeth 424, 434 on the threaded gearedsleeves 420, 430 can be engaged by the worm 440 at the same time alongthe pressure angle ANG, as shown in FIGS. 12A and 12B. Distributing thedistraction load over multiple teeth of the sleeves 420, 430 and theworm 440 is critical to achieve the minimum device size while providinga maximum amount of distraction and load capacity.

In one embodiment, a distractible intervertebral body fusion devicesimilar to device 400 can include a two part worm that provides fordifferential distraction of the device. One example of such a device isdisclosed in U.S. Patent Application Publication No. 2011/0160861, theentire disclosure of which is incorporated by reference herein. The twopart worm can include a first portion having a first threaded sectionfor engaging a first threaded geared sleeve and a second portion havinga second threaded section for engaging second threaded geared sleeve. Inone embodiment, the two portions of the worm are connected to eachother. The two portions of the worm rotate independently of each other.Thus, each threaded geared sleeve can be rotated separately to bedistracted different amounts, which provides the ability to angle thetop member of the device. Such a configuration can accommodate lordoticor kyphotic geometry. An inserter to distract such a device canotherwise have similar features to the inserters described herein butinclude a pair of drive shafts. In one embodiment, each drive shaft canbe operably connected to a different actuation mechanism. Such aninserter would therefore include three elongate shafts—a single supportshaft and a pair of drive shafts.

In one embodiment, distractible intervertebral body fusion devices asdescribed herein can be made of titanium and the deliverysystem/introducer can be made primarily out of stainless steel.Components of each mechanism that slide against each other can be madeof different types of the general material. For example, the firstmember can be made from Ti 6A1 4V standard titanium, which has highsmooth fatigue performance, while the threaded geared sleeves can bemade from Ti 6A1 4V ELI, which has high notched fatigue performance.Such a combination results in each component being made out of apreferred material for its fatigue notch factor while the overallmechanism implements different materials where components are slidablyarranged.

In various embodiments, device is shaped to be ergonomic. Device canhave various shapes, such as, for example, rectangular, kidney, orfootball shaped. A kidney or football shaped device maximizes contactbetween the device and the vertebral bodies because the end plates ofvertebrae tend to be slightly concave. One or both ends of the devicemay also be tapered in order to facilitate insertion. This minimizes theamount of force needed to initially insert the device and separate thevertebral bodies. In addition, the device may be convex along both itslength and its width, or bi-convex. Device can be constructed in varioussizes depending on the type of vertebra and size of patient with whichit is being used.

Device can be manufactured in various ways with, in some embodiments,different components of the device can be manufactured in differentways. In one embodiment, thread milling can be implemented tomanufacture the various threads in device. Wire EDM can be utilized tomanufacture some or all of the holes and openings in the device.Assembly jigs and post processing steps can also be utilized to allowthe device to be manufactured to exacting standards.

In one embodiment, the surface of the device can be treated to minimizesurface roughness or to reduce pitting of the material within the body.A rough surface or pits can increase the stress on the device, which canresult in shortening of the fatigue life and/or reduce fatigue strength.In one embodiment, the surface can be treated with electro-polishing,both removing burrs from the edges of the device and finishing thesurface. In another embodiment, the surface can be left untreatedbecause a rough surface on the end plates helps prevent accidentalextrusion of the device. In one embodiment, the device can also becoated with a highly elastic, impermeable material to extend its fatiguelife. Specifically, the impermeable material would prevent the corrosiveproperties of blood from degrading the device. In another embodiment,the device can be comprised of a biocompatible material, so that nocoating is necessary. In a further embodiment, the device can be made ofa biodegradable material designed to degrade in the body at a selectedstage of the healing process, such as after bone fusion.

Referring to FIGS. 13A-13C and 14A-14B there can be seen a distractibleintervertebral body fusion device 500 according to an aspect of thepresent invention that can be inserted and distracted with an introduceras described herein. Device 500 includes a device body 502. Device body502 can include a nose portion 504, a rear portion 506, a pair ofopposed end plates 508, structural members 510 and flexure members 512attaching one end of the structural members 510 to end plates 508 andthe other end of structural members 510 to blocks 514 a, 514 b. Furtherdetails regarding distractible intervertebral body fusion devices suchas device 500 can be found in U.S. Patent Application Publication No.2010/0185291, which is hereby incorporated by reference herein.

Device body 502 can include two sets of structural members 510, orstruts, on each side (FIGS. 13A-13D) or can include three, or more, setsof structural members 510 on each side (FIGS. 14A-14B). As will bediscussed in more detail herein, addition of a third strut providesgreater stability to the device 500. Flexure members 512 are thin stripsof material that connect the structural members to the end plates 508and expansion blocks 514. The flexure members 512 allow a one-piecedevice 500 to behave similarly to a device having multiple parts and arotating pin joint. Flexure members 512 can, for example, be bandflexures (FIGS. 13A-13C and 14A-14B), circular flexures, ellipticalflexures, or leaf flexures.

In one embodiment, each end plate 508 includes a rectangular opening516. Opening can be used to facilitate bone growth through the device500. In other embodiments, opening 516 can be filled with a gel, rubber,or other complaint material that can replicate the nucleus of aninterverterbral disc and supplement the strength of the flexures 512 incompressive, shear, and torsional loading conditions. Alternatively, agenerally solid surface or a surface with multiple openings can beprovided on each end plate 508. End plates 508 can have a rough surfaceor teeth to create friction with the end plates of the vertebra toprevent accidental extrusion of the device 500. In one embodiment, thedevice body 502, or portions of the device body 502, can be overmoldedwith a polymer or other material to supplement the strength of thedevice. For example, long carbon nanotube chains can be applied to thesurface of the device so that as the device distracts the carbonnanotubes align along the surface of the flexures to add to thestability of the device.

Nose portion 504 can be tapered to facilitate the insertion of thedevice 500 into the disc space. Rear portion 506 can also be tapered. Inone embodiment, nose portion 504 and rear portion 506 can be left opento accommodate a tapered delivery shaft of an introducer that can extendall the way through the device 500.

Drive screws 518 can be inserted through guide apertures 520 in rearportion 506 and through expansion blocks 514. Actuation of drive screws518, such as by an introducer as described herein, drives blocks 514closer together, which causes deflection of the flexure members 512,resulting in expansion of the structural members 510 and distraction ofthe end plates 508. In one embodiment, blocks 514 b in FIGS. 13A-13C canbe tapped to accommodate drive screws 518 and blocks 514 a can provide aclearance fit with screws 518. When drive screws 518 are actuated, thisallows blocks 514 a to be pulled towards blocks 514 b, causing thedevice 500 to distract. Similarly, blocks 514 a and 514 c in FIGS.14A-14B can be tapped and blocks 514 b can provide a clearance fit. Insuch a configuration, the opposite end from the hex of screws 518 canhave a shoulder to draw block 514 b towards blocks 514 c and 514 a. Insome embodiments, mechanisms other than drive screws can be used todistract device. Such mechanisms include, for example, a pop-rivetmechanism, a sardine key and ribbon, a tourniquet and wire, a sawblade/ratchet, and shape changing materials such as a shape memory alloyor a conducting polymer actuator. The rear block can include aprojection for engaging the teeth of the drive mechanism. In oneembodiment, piezo-electric inch-worm motors can be used to actuate themovement of blocks 514. In another embodiment, a balloon can be insertedinto device and inflated to expand the device. The balloon can remain inthe device and function like the nucleus of a disc.

In various embodiments, device body 502 is shaped to be ergonomic.Device body 502 can have various shapes, such as, for example,rectangular, kidney, or football shaped. A kidney or football shapeddevice body 502 maximizes contact between the device and the vertebralbodies because the end plates of vertebrae tend to be slightly concave.One or both ends of the device may also be tapered in order tofacilitate insertion. This minimizes the amount of force needed toinitially insert the device and separate the vertebral bodies. Inaddition, the device may be convex along both its length and its width,or bi-convex. Device 500 can be constructed in various sizes dependingon the type of vertebra and size of patient with which it is being used.

Device body 502 can also be comprised of various materials. In oneembodiment, device is comprised of a ductile material. Such materialscan include, for example, titanium, nitinol, and thermoplastics. In someembodiments, the material near the ends of the flexures 512 can becold-worked to increase the stiffness of the device as it distracts.Heat treating could also be used to alleviate machining stresses andcould be followed by hardening treatment to make the device stiffer.Additionally, in some embodiments the flexures can be affixed to thedevice in subsequent manufacturing steps in order to permit the flexuresto be made from a different material or materials, or materials treateddifferently, than the structural members and end plates of the device.Flexures could also be laminated beams having a core of another stiffmaterial, a soft material such as a foam, or an open core. Having a softor open core would allow the flexures to effectively decrease inthickness as they are bent around the curved surfaces of the struts.This would decrease the amount of strain present in the flexure due tobending, allowing the device to accommodate greater functional loading.

Device 500 can be inserted with tapered nose portion 504 first. In oneembodiment, a working channel of 8-26 mm is required for insertion ofthe device. One device 500 can be inserted, or, for additional support,two devices 500 can be inserted. Two devices 500 can be especiallyuseful for treating larger patients in which the device may encounterhigher loads. In another embodiment, three or more small devices can beinserted into the disc space in order to very accurately control theorientation and distance between discs. Three or more distractionmechanisms may be positioned circumferentially between two circularendplates to result in very accurate control and orientation of the endplates. Such a device would resemble a hexapod. In another embodiment,two or more devices may be mated or assembled in the disc space to workcongruently in performing distraction either in height or width.

Once inserted in the disc space, an insertion tool or introducer asdescribed herein can be actuated to rotate drive screws 518. Drivescrews 518 can be actuated from the rear of device 500 to allowinsertion tool to reposition or, if necessary, remove device 500 priorto disengaging from device 500. Drive screws 518 can be actuated thesame amount for uniform distraction on both sides of an embodiment withtwo drive screws or may be actuated different amounts for non-uniformdistraction with one side of the device 500 higher than the other.Non-uniform distraction causes torsional forces on flexures.Alternatively, an embodiment can be driven with a single flexure andsingle drive screw or with multiple flexures multiplexed to a singledrive screw arrangement.

Unlike many common scissor jacks, such as, for example, car jacks,device 500 can easily be distracted from its lowest, or most compressed,state. This is because the flexure members 512 on each end of a givenstructural member are oriented such that the tensile loads on theflexures do not act towards each other, but instead pass by each other,like passing cars (see arrow A and arrow B in FIG. 13B). Common jacks,which do not utilize flexure members, may have difficulty distractingfrom the lowest state because the tensile loads can act “heads on” witheach other, putting the device under strong internal horizontalcompression but without a significant force component in the verticaldirection at the lowest state that can easily initiate distraction. Thetension in the flexure member required to support a compressive load isequal to the compressive load multiplied by the cosine of the angle ofthe rigid link divided by the sine of the rigid link. Because the sineof zero degrees, the angular position of normal scissor jacks in thecompressed state, is equal to zero, the force required for initialdistraction can be effectively very large. The rigid links of the deviceof various embodiments of the present invention may start off in theposition of zero angular position, but because the flexure members areon opposing sides of the rigid links the effective angular position isnon-zero, making the force required for initial distraction finite andgenerally smaller than a conventional scissor jack.

As drive screws 518 are actuated, the device 500 is distracted as shownin FIGS. 15 and 16. Drive screws 518 (not shown in FIGS. 15 and 16)drive expansion blocks 514 together, which cause flexure members 512 todeflect thereby expanding structural members 510 to distract end plates508. Referring now to FIGS. 17A-17D, FIGS. 17A and 17D depict a flexuremember 512 and structural member 510 before distraction, whereas FIGS.17B and 17C depict after distraction. Each flexure member 512 beginswrapped around the curved end of the structural member 510. Note in FIG.17A that the flexure 512 rests on the structural member 510. This allowsthe device 500 to carry a large compressive load in the compressed statewithout greatly deforming the flexure 512. As the structural members 510are distracted, the flexure members 512 bend towards flat. In thisembodiment, the flexure members 512 do not bend all the way flat,however, even at maximum distraction of the end plates 508, because theycontact curved backstop 522. This allows the device 500 to carry a largecompressive load in the distracted state without further deforming theflexure 512. Curved backstop 522 has a “frowning eyebrows” configurationin order to provide opposed curved surfaces for opposing flexure members512. Because the flexure members 512 do not have to bend until they arecompletely flat to reach complete distraction, the amount of strain onthe flexure members 512 necessary for complete distraction is minimized.The likelihood of device failure is therefore reduced.

FIGS. 17E-17G depict the behavior of flexures as the device isdistracted. Flexure member 512 defines a first open area, or kerf 540 a,between curved backstop 522 and flexure member 512 and a second kerf 540b between inner perimeter 542 of structural member 510 and flexuremember 512. When device 500 is in a collapsed configuration (FIG. 17E),kerf 540 a is wider than kerf 540 b. As device distracts, flexure member512 flattens out towards curved backstop 522, so kerf 540 b widens askerf 540 a narrows. The fulcrum around which flexure member 512 bends isshown by arrows 544 a and 544 b. As can be seen in FIGS. 17E-17G, thefulcrum 544 a, 544 b translates along the flexure member 512 as itbends. Fulcrum 544 a, 544 b therefore travels in both vertical andhorizontal directions. This provides for increased distraction of thedevice. As the fulcrum 544 a, 544 b moves along the flexure member 512as the device distracts, a greater portion of the compressive load onthe device 500 is supported by the structural member 510 and,accordingly, the tensile forces on the flexure member 512 are reduced.The device 500 of this embodiment is therefore strongest when it isfully distracted.

In various embodiments, distractible intervertebral body fusion devicehas a one-piece device body that can be manufactured in a distracted orpartially distracted state. This provides great cost savings overdevices that require multiple pieces to be separately manufactured andassembled. Manufacturing in the distracted state provides additionalclearance for assembly and for access by manufacturing tools, the sizeof which is inversely proportional to the cost of manufacturing. Inaddition, when the device is manufactured in the distracted state, thedevice can be compressed into a position of minimal height whilecompressive stress remains in the flexure members. This compressivestress results in a negative mean stress, which can extend the fatiguelife of the device. In one embodiment, the device can be manufacturedusing wire or sink edm. In another embodiment, the device can bemanufactured using three-dimensional printing techniques or the like. Insome embodiments, portions of the flexures can be machined separatelyand welded to the device. This allows for flexures that have zero kerfand rest completely against the backstops once distracted.

In one embodiment, the surface of the device can be treated to minimizesurface roughness or to reduce pitting of the material within the body.A rough surface or pits can increase the stress on the device, which canresult in shortening of the fatigue life and/or reduce fatigue strength.In one embodiment, the surface can be treated with electro-polishing. Inanother embodiment, the surface can be left untreated because a roughsurface on the end plates helps prevent accidental extrusion of thedevice. In one embodiment, the device can also be coated with a highlyelastic, impermeable material to extend its fatigue life. Specifically,the impermeable material would prevent the corrosive properties of bloodfrom degrading the device. In another embodiment, the device can becomprised of a biocompatible material, so that no coating is necessary.In a further embodiment, the device can be made of a biodegradablematerial designed to degrade in the body at a selected stage of thehealing process, such as after bone fusion.

Numerous other types of supports may be used with the device. Supportscan be used to supplement the compressive strength, bending, ortorsional strength of device. In one embodiment, one or more rigidsupports can be inserted into the open space between end plates afterdistraction to help keep the end plates in their distracted state. Inanother embodiment, chocks can be placed at the intersection ofstructural members in each strut to provide further support for struts.In a further embodiment, a rod and screws can be used with the device aspart of an assembly affixed to the vertebral body.

Various embodiments of systems, devices and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the present invention. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, implantation locations, etc. have been described for use withdisclosed embodiments, others besides those disclosed may be utilizedwithout exceeding the scope of the invention.

1. An inserter for inserting and expanding a distractible intervertebralbody fusion device into an intervertebral disc space defined betweenadjacent vertebrae of a patient, comprising: a shaft frame having aproximal end and a distal end; a drive shaft assembly extending from thedistal end of the shaft frame, the drive shaft assembly adapted to beattached to a distractible intervertebral body fusion device such thatrotation of the drive shaft assembly causes the device to expand betweena compressed configuration and an expanded configuration; a supportshaft assembly extending from the distal end of the shaft frame adjacentthe drive shaft assembly, the support shaft assembly adapted to beattached to the distractible intervertebral body fusion device tostabilize the device as the drive shaft assembly is rotated to expandthe device; and a drive housing operably connected to the shaft frameand extending outwardly from the shaft frame distally of the proximalend of the shaft frame, the drive housing providing access into theshaft frame to a proximal end of the drive shaft assembly.
 2. Theinserter of claim 1, further comprising an actuation tool disposedwithin the drive housing, the actuation tool extending through theaccess into the shaft frame to interface with the proximal end of thedrive shaft assembly.
 3. The inserter of claim 2, wherein the proximalend of the drive shaft assembly comprises a shaft gear and a distal endof the actuation tool includes a drive gear that meshes with the shaftgear, and wherein activation of the actuation tool causes a rotation ofthe drive gear that thereby causes a rotation of the shaft gear torotate the drive shaft assembly.
 4. The inserter of claim 2, wherein theactuation tool is an electric screw driver.
 5. The inserter of claim 1,wherein the drive shaft assembly includes a joint extending from thedistal end of the shaft frame and a drive link extending distally fromthe joint.
 6. The inserter of claim 5, wherein one of the joint and thedrive link includes a slot to which the other of the joint and the drivelink is connected with a pin, the slot allowing relative longitudinalmovement of the joint and the drive link.
 7. The inserter of claim 6,further comprising a biasing member disposed on one of the joint and thedrive link, the biasing member biasing the relative longitudinalmovement of the joint and the drive link.
 8. The inserter of claim 1,further comprising a device interface positioned adjacent a distal endof the drive shaft assembly and a distal end of the support shaftassembly, the device interface including a pair of apertures, one of thedrive shaft assembly and the support shaft assembly extending througheach aperture.
 9. The inserter of claim 8, wherein the device interfacehas a distal surface at least a portion of which is shaped to conform toan outer surface of a particular distractible intervertebral body fusiondevice for insertion into the disc space.
 10. The inserter of claim 1,wherein the shaft frame includes markings indicating a height of adistractible intervertebral body fusion device that is distracted byrotation of the drive shaft assembly.
 11. The inserter of claim 10,wherein the shaft frame includes a longitudinal slot along which theheight markings are located, and further comprising a block stopselectively positionable along the slot, the block stop preventingfurther rotation of the drive shaft assembly when the distractibleintervertebral body fusion device has reached the height indicated bythe marking at which the block stop is located.
 12. An inserter forinserting and expanding a distractible intervertebral body fusion deviceinto an intervertebral disc space defined between adjacent vertebrae ofa patient, comprising: a shaft frame having a proximal end and a distalend; means for expanding a distractible intervertebral body fusiondevice between a compressed configuration and an expanded configurationextending from the distal end of the shaft frame; means for stabilizingthe distractible intervertebral body fusion device as the means forexpanding is used to expand the device, the means for stabilizingextending from the distal end of the shaft frame adjacent the means forexpanding; and a drive housing operably connected to the shaft frame andextending outwardly from the shaft frame distally of the proximal end ofthe shaft frame, the drive housing providing access into the shaft frameto a proximal end of the means for expanding.
 13. The inserter of claim12, further comprising means for rotating the means for expandingdisposed within the drive housing, the means for rotating extendingthrough the access into the shaft frame to interface with the proximalend of the means for expanding.
 14. The inserter of claim 13, wherein adistal end of the means for rotating includes a drive gear that engagesthe proximal end of the means for expanding, and wherein activation ofthe means for rotating causes a rotation of the drive gear that therebycauses a rotation of the means for expanding.
 15. The inserter of claim12, further comprising a device interface positioned adjacent a distalend of the means for expanding and a distal end of the means forstabilizing, the device interface including a pair of apertures, one ofthe means for expanding and the means for stabilizing extending througheach aperture.
 16. The inserter of claim 15, wherein the deviceinterface has a distal surface at least a portion of which is shaped toconform to an outer surface of a particular distractible intervertebralbody fusion device for insertion into the disc space.
 17. The inserterof claim 12, wherein the shaft frame includes means for indicating aheight of a distractible intervertebral body fusion device that isexpanded by the means for expanding.
 18. The inserter of claim 17,wherein the shaft frame further comprises a means for preventing furtherexpansion of the device beyond a predetermined maximum height indicatedby the means for indicating.
 19. A method comprising: providing adistractible intervertebral body fusion device, the device expandablebetween a compressed configuration and an expanded configuration;providing an inserter having a shaft frame with a distal end and aproximal end, a drive shaft assembly extending from the distal end ofthe shaft frame, a support shaft assembly extending from the distal endof the shaft frame, and a drive housing operably connected to the shaftframe and extending outwardly from the shaft frame distally of theproximal end of the shaft frame, the drive housing providing access intothe shaft frame to a proximal end of the drive shaft assembly; providingan actuation tool; and providing instructions for implanting thedistractible intervertebral body fusion device into a disc spaceprovided between adjacent vertebrae of a patient with the inserter andactuation tool, the instructions comprising: inserting the actuationtool into the drive housing such that the actuation tool interfaces withthe proximal end of the drive shaft assembly; attaching a distal end ofthe drive shaft assembly to the distractible intervertebral body fusiondevice; attaching a distal end of the support shaft assembly to thedistractible intervertebral body fusion device; inserting thedistractible intervertebral body fusion device into the disc space withthe inserter; and activating the actuation tool to rotate the driveshaft assembly to expand the distractible intervertebral body fusiondevice from the compressed configuration to the expanded configuration.20. The method of claim 19, wherein the step of interfacing theactuation tool with the proximal end of the drive shaft assemblyincludes interfacing a drive gear at a distal end of the actuation toolwith a shaft gear at the proximal end of the drive shaft assembly, andwherein the step of activating the actuation tool to rotate the driveshaft assembly includes rotating the drive gear to cause a rotation ofthe shaft gear.
 21. The method of claim 19, wherein the step ofproviding an actuation tool includes providing an electric screwdriver.22. The method of claim 19, further comprising providing a plurality ofdevice interfaces, the plurality of device interfaces having more thanone different configuration with each device interface having a distalsurface at least partially shaped to conform to an outer surface of aparticular type of intervertebral body fusion device, and wherein theinstructions further comprise: selecting a device interface from theplurality of device interfaces with a configuration shaped to conform toa type of intervertebral body fusion device of the providedintervertebral body fusion device; and attaching the device interface tothe drive shaft assembly and support shaft assembly adjacent the distalends of the drive shaft assembly and support shaft assembly, and whereinthe steps of attaching the drive shaft assembly and support shaftassembly to the intervertebral body fusion device include interfacingthe distal surface of the device interface with the intervertebral bodyfusion device.
 23. The method of claim 19, wherein the shaft frameincludes a longitudinal slot and markings along the slot indicating aheight of the distractible intervertebral body fusion device as it isexpanded by the inserter and the inserter includes a block stopselectively positionable along the slot, and wherein the instructionsfurther comprise: sliding the block stop along the slot and fixing theblock stop in place at a maximum desired expanded height of theintervertebral body fusion device, and the step of activating theactuation tool to rotate the drive shaft assembly to expand thedistractible intervertebral body fusion device from the compressedconfiguration to the expanded configuration includes activating theactuation tool until the block stop prevents further rotation of thedrive shaft.
 24. The method of claim 20, wherein the step of insertingthe distractible intervertebral body fusion device into the disc spaceincludes striking the proximal end of the shaft frame with a hammer ormallet.